Navy Lieutenant Clea Thorson is running away from something. She looks back over her shoulder but no one seems to be pursuing her. She steps in front of a bus and is killed. The NCIS crew arrives on the scene. Lt. Thorson has complex calculations written on her body. Paper in short supply? When Clea is brought to Dr. Ducky Mallard's autopsy table, Abby (Pauley Perrette) photographs the writing. She says she sees a pattern to it.

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Tony DiNozzo (Michael Weatherly) is on his phone talking to his new girlfriend about their upcoming Halloween date. Her name is Ethel, which leads Tim McGee to make wisecracks. Tony says he likes the name.

"It's strong and distinguished. It says ...," Tony begins.

"I've fallen and I can't get up," McGee supplies.

Ziva David laughs. Tony tells them he thinks he and Ethel really have something.

"They have antibiotics for that Tony," McGee comments dryly.

Nice going McSarcasm.

Lt. Thorson attended MIT and was a civil engineer in the Navy. This is one smart gal. If you saw the Ron Howard directed movie "A Beautiful Mind" you can draw your own parallels.

Thorson was hired and fired by GEN-1 Biotech, Inc. Her boss, Martin Stillwell sent her a threatening video message. Thorson has no human ties except her mother and no home address. McGee does find a bank account with large deposits during the two weeks after she was fired. Nice to have something to fall back on.

Ducky informs Leroy Jethro Gibbs (Mark Harmon) that Clea was very sick. That caused her death, not being struck by the bus. She died of organ failure due to being poisoned. Ducky has no idea how the poison was administered.

Tony and Ziva confront Stillwell and meet her co-worker and friend April Ferris. Clea's project was to find a way to help the Navy go green. No more dependence on foreign oil made the project very lucrative.

Clea's mother arrives and tells Gibbs her daughter was on meds. She suffered mood swings, manic episodes and insomnia. Her meds adjusted, everything was fine with Clea until the last couple of weeks. She wasn't the same as before.

Abby is drawn to Clea's case. She idolizes this woman for her scientific abilities and amazing mind. Abby becomes obsessed with finding the answer to Clea's murder through the equations she left behind.

Chaos Theory

Tony and Ziva find the bunker where Thorson had locked herself away. Formulas are written on every surface. They bring in Abby who is astounded. She comments she has never seen anyone so focused. McGee tells her he has, alluding to Abby. She dismisses him. Darn. I was hoping for a McAbby moment.

The bunker has several cameras suggesting paranoia. Ziva finds a journal with references to a mysterious Mr. K. Tony finds bottles of meds and puts forth the idea the paranoia might be drug induced. This bothers Abby who asks for respect for Clea. The hard drive on her computer has been erased. Someone was stealing Clea's work. That work would make billions for some company. The security cameras only show her in her bunker shut away from the world doing the same routine every day. She eats at the same time, works on schedule and showers at the same time. How very OCD.

Ducky comes across Abby in his autopsy room speaking to Clea. She says she is a kindred spirit and will discover the answer for her murder. The next day McGee finds Abby in her lab fired up on Caf-Pows after spending the entire night trying to crack the codes. She tells McGee she needs to understand Clea better. Using her journal as a guide Abby and McGee retrace her steps taking several buses. McGee loses Abby at one point. She keeps going until she finds Clea's mentor Professor Daniel Redner. He gives Abby a book, Walt Whitman's Leaves Of Grass, which he and Clea read during her visits.

Tony shows Gibbs a video of Lt. Thorson at a coffee shop. She is arguing loudly with someone only she can see. She does so for an hour every day. Is this the mysterious Mr. K?

Someone has to tell Abby. When she appears in the office Gibbs has to raise his voice to stop her racing through her visit with Professor Redner. She is stunned by this but more so when he shows her Thorson fighting with her hallucination. Abby is angry and tells everyone they don't understand. She locks herself in her lab.

Clea's formula is the key to solving both murders. Abby needs to figure it out. Gibbs brings in Mrs. Thorson to talk with Abby. She tells her to remove all emotion. Abby has to let go of Clea and look at the equations as a pure scientist. Abby goes back to being Abby. She identifies a leaf drawn in the corner of a whiteboard Clea had written on. She shakes Leaves Of Grass. A memory card falls out. McGee pops it in the computer finding Clea's formula for green energy. E. coli plus photosynthesis makes carbon dioxide, which makes energy, and I have no idea what I'm talking about. Whatever, but apparently it is worth billions to Avaxis, the company she was developing it for. Systems Director Rupert Kritzer is Mr. K. The guy was real after all. Kritzer is brought in for interrogation but is not the killer.

McGee finds a canister with poison that fed into the water system for Clea's daily shower. She was slowly poisoned over a period of two weeks. With Stillwell and Clea dead April Ferris in now head of GEN-1. She killed her way to the top.

Back at NCIS Tony appears in his costume for his Halloween date with Ethel. OMG, Tony is Tony! He is dressed as Tony Manero from Saturday Night Fever. Sorry, Tony, but John Travolta you ain't. Tony in white, tight polyester? Now that's scary.

Was "Cracked" equal to other episodes you've seen this season? Let me know by adding your thoughts in the comment section.